Commit b2deabe3 authored Nov 14, 2012 by Mark Rutland

arm: arch_timer: add arch_counter_set_user_access



Several bits in CNTKCTL reset to 0, including PL0VTEN. For architectures
using the generic timer which wish to have a fast gettimeofday vDSO
implementation, these bits must be set to 1 by the kernel. For
architectures without a vDSO, it's best to leave the bits set to 0 for
now to ensure that if and when support is added, it's implemented sanely
architecture wide.

As the bootloader might set PL0VTEN to a value that doesn't correspond
to that which the kernel prefers, we must explicitly set it to the
architecture port's preferred value.

This patch adds arch_counter_set_user_access, which sets the PL0 access
permissions to that required by the architecture. For arch/arm, this
currently means disabling all userspace access.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>

parent 1ba1cefc

arch/arm/include/asm/arch_timer.h

+12 −0

Original line number	Diff line number	Diff line
		@@ -106,6 +106,18 @@ static inline u64 arch_counter_get_cntvct(void)
		asm volatile("mrrc p15, 1, %Q0, %R0, c14" : "=r" (cval));
		return cval;
		}

		static inline void __cpuinit arch_counter_set_user_access(void)
		{
		u32 cntkctl;

		asm volatile("mrc p15, 0, %0, c14, c1, 0" : "=r" (cntkctl));

		/* disable user access to everything */
		cntkctl &= ~((3 << 8) \| (7 << 0));

		asm volatile("mcr p15, 0, %0, c14, c1, 0" : : "r" (cntkctl));
		}
		#else
		static inline int arch_timer_of_register(void)
		{

arch/arm/kernel/arch_timer.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -155,6 +155,8 @@ static int __cpuinit arch_timer_setup(struct clock_event_device *clk)
		enable_percpu_irq(arch_timer_ppi[PHYS_NONSECURE_PPI], 0);
		}

		arch_counter_set_user_access();

		return 0;
		}